Certain abbreviations that may be found in the description and/or in the Figures are herewith defined as follows:
3GPP Third Generation Partnership Project
ACK acknowledgment
AMC adaptive modulation and coding
BPSK binary phase shift keying
BW bandwidth
CAZAC constant-amplitude zero auto-correlation
CDM code division multiplexing
CP cyclic prefix
CQI channel quality indicator
E-UTRAN evolved UTRAN
FBI feedback information
FDM frequency division multiplexing
FDMA frequency division multiple access
FFT fast Fourier transform
HARQ hybrid automatic repeat request
IFFT inverse FFT
L1 Layer 1 (physical layer)
L2 Layer 2 (data link layer)
LB long block
LTE long term evolution
MCS modulation coding scheme
NACK negative ACK
Node-B Base Station
eNB EUTRAN Node B
OFDM Orthogonal Frequency Domain Multiplex
PAPR peak to average power ratio
PRB physical resource block
PUCCH physical uplink control channel
QPSK quadrature phase shift keying
SB short block
SC-FDMA single carrier, frequency division multiple access
SF spreading factor
SINR signal-to-interference and noise ratio
TDM time division multiplexing
TTI transmission time interval
UE user equipment
UL uplink
UTRAN universal terrestrial radio access network
ZAC zero autocorrelation sequence
A proposed communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE) is currently under discussion within the 3GPP. The current working assumption is that the DL access technique will be OFDM, and the UL technique will be SC-FDMA.
Control channel multiplexing is performed in the UTRAN-LTE system, including control channel multiplexing in the SC-FDMA based UL. There are two different type of control signals to be carried in the UL:
1. Data associated control signaling including transport format and HARQ information. This information is associated with UL data transmissions.
2. Data-non-associated control signaling, such as CQI and/or ACK/NACK due to downlink transmissions.
Of particular interest to this discussion is the data-non-associated control signaling, the transmission of which may be divided into two separate classes:
a) data-non-associated control signaling multiplexed with UL data; and
b) data-non-associated control transmitted without UL data.
Of further particular interest to this discussion is the data-non-associated control signaling without UL data (class b above).
Reference in this regard may be had to 3GPP TR 25.814, v7.0, Section, 9.1.1.2.3, Multiplexing of L1/L2 control signaling, where it is stated that there are three multiplexing combinations for the uplink pilot, data, and L1/L2 control signaling within a sub-frame that are considered for a single UE:
multiplexing of pilot, data, and data-associated L1/L2 control signaling;
multiplexing of pilot, data, and data-associated and data-non-associated L1/L2 control signaling; and
multiplexing of pilot and data-non-associated L1/L2 control signaling.
In single-carrier FDMA radio access, time-domain multiplexing is used for the above-mentioned three multiplexing combinations in order to retain the advantageous single-carrier feature with a low PAPR.
Both data-associated and data-non-associated control signaling are time-multiplexed with data and pilot within the sub-frame. Furthermore, the data-associated and data-non-associated control signaling from multiple UEs are multiplexed in the frequency or/and code domains associated with multiple pilot channels.
The data-non-associated control signaling can also be time-multiplexed with data if the UE has UL data transmission. Meanwhile, the data-non-associated control signaling for that transmit only the L1/L2 control, is multiplexed exclusively in a semi-statically assigned time-frequency region. This channel is called as PUCCH (Physical Uplink Control Channel) in current LTE terminology. The data-non-associated control signaling of different UEs is multiplexed using the frequency/time/code domain, or a hybrid of them, within the assigned time-frequency region. The exclusive time-frequency region can be separated into multiple separated frequency-time resources. The possibility for multiplexing of data-non-associated control signaling with data channel by exclusive frequency resource, i.e., frequency-multiplexing, is for further study.
FIG. 1 herein reproduces a part of Figure 9.1.1.23-2 of 3GPP TR25.814, “Multiplexing scheme for L1/L2 control signaling, data, and pilot”, and assumes that data-non-associated control signaling for UEs that transmits only the L1/L2 control, is multiplexed exclusively in a semi-statically assigned time-frequency region (denoted with the asterisk in FIG. 1). On the contrary, UEs which have both UL data and data-non-associated control signaling utilize time-multiplexing between control and data.
An assumption may be made that the amount of data to be carried in the considered resource varies between 1-30 bits. For example, three different cases may exist: ACK/NACK only; CQI only; and ACK/NACK+CQI. However, L1 feedback (FB), needed by various MIMO and closed loop beamforming techniques, may also be considered.
It has been assumed that dedicated frequency/time resource for shared control channel requires (at least) two PRBs (360 kHz) per 5 MHz BW (overhead=8%). The target has been that at least 12 users/TTI should be orthogonally multiplexed for the given resource (simultaneously).
A problem that arises is how to multiplex a sufficient amount of UEs into the pre-determined resources in such a way that the control information can be conveyed in a reliable fashion on the UL.
Several contributions on data-non-associated channel multiplexing have been proposed thus far during the 3GPP standardization process for UTRAN-LTE.
For example, in R1-061862, “Uplink Non-data-associated Control Signaling”: Ericsson, Jun. 27-30, 2006, it is proposed to have a new sub-frame format with an additional short block for data-non-associated control signaling. At least one perceived problem with this proposal, however, is that the scalability of the resource is less than optimum.
Also by example, in R1-062065, “L1/L2 UL Control Mapping and Numerology”: Motorola, Aug. 28-Sep. 1, 2006, it is proposed to have a FDM-type of multiplexing combined with frequency hopping within a sub-frame. At least one perceived problem with this proposal is that the number of active sub-carriers is only two, which can lead to very high power differences between UEs occupying a large bandwidth. Thus, there is an increased probability that intra-cell orthogonality would be lost at least to some extent under practical transmission conditions, such as those where frequency and timing errors exist.
Section 9.1.1 of 3GPP TR 25.814, v7.0 is incorporated by reference.